I - In any population variation exists. Most bacteria die when exposed to an antibiotic but some survive because they are resistant. They survive and reproduce.
II - In a population of bacteria that are exposed to antibiotics some bacteria are able to change their genetic make-up and survive. The new genotype is passed on to offspring.
III - There is a change in the environment when an antibiotic is added. Some of the bacteria adapt to the new environment. They survive and reproduce.
Scientists would explain how natural selection contributes to antibiotic resistance by showing that in a population of bacteria exposed to antibiotics, those with genetic variations that make them resistant to the antibiotics survive and reproduce. This resistance can be passed on to future generations, leading to an increase in antibiotic-resistant bacteria in the population due to natural selection.
Disease and Natural Selection
One type of natural selection is called frequency-dependent selection. This type of selection favors phenotypes that are either common, positive frequency-dependent selection. or rare, negative frequency-dependent selection. An example of negative frequency-dependent selection can be observed in the interaction between the human immune system and various infectious agents such as bacteria or viruses. As a human population is infected by a common strain of bacteria or virus, the majority of individuals in the population become immune to it, either naturally or through the use of antibiotics and/or vaccinations. This then selects for rarer strains of the bacteria or virus. which can still infect the population because of mutations. The new strains have greater evolutionary fitness because they are less common.
Question 1
Consider the model of bacterial resistance to antibiotics. Use the Roman numerals (I - III) to guide you through the steps, describe how a scientists would explain how natural selection contributes to antibiotic resistance.
Responses
A There is a change in the environment when an antibiotic is added. Some of the bacteria adapt to the new environment. They survive and reproduce.There is a change in the environment when an antibiotic is added. Some of the bacteria adapt to the new environment. They survive and reproduce.
B In any population variation exists. Most bacteria die when exposed to an antibiotic but some survive because they are resistant. They survive and reproduce.In any population variation exists. Most bacteria die when exposed to an antibiotic but some survive because they are resistant. They survive and reproduce.
C In a population of bacteria that are exposed to antibiotics some bacteria are able to change their genetic make-up and survive. The new genotype is passed on to offspring.In a population of bacteria that are exposed to antibiotics some bacteria are able to change their genetic make-up and survive. The new genotype is passed on to offspring.
D Sexual reproduction of bacteria cause variations. Some bacteria survive antibiotics and some do not. Eventually because of sexual reproduction over time all of the bacteria will become extinct.
1 answer